Recently, we have demonstrated that treatment with cyclic AMP of microsomal preparations from rat aorta augments calcium sequestration. Since aortic microsomes have been found to contain an appreciable amount of cyclic AMP-dependent protein kinase activity, we believe that alterations in the vascular tonicity as a result of calcium translocations is brought about by phosphorylation of serine residues in a microsomal protein component with a molecular weight of 44,000 daltons. Both the catalytic and regulatory subunits influence the kinase activity. Therefore, the study to understand the mechanism of enzyme regulation by conformational changes induced by subunit interactions is a considerable importance. The broad objectives of this proposal are to purify both isoenzymic forms of cyclic AMP-dependent protein kinase from bovine carotid artery to homogeneity and resolve the holoenzyme into catalytic and regulatory subunits. Characterize the native as well as the subunits component by various physical-chemical methods to determine their a) pI, molecular weights, sedimentation coefficients, diffusion coefficients, and other hydrodynamic properties. Compare the protein kinase characteristics from cardiovascular tissues of spontaneously hypertensive and Kyoto Wistar normotensive rats. BIBLIOGRAPHIC REFERENCES: Bhalla, R.C., R.C. Webb and Tommy Brock: Cyclic AMP-dependent-protein kinase activity in blood vessels of spontaneously hypertensive rats. Fed. Proc. 35, 1064, 1976.